The present invention relates to pneumatic tires and more particularly, to a method of forming puncture preventing layer on an inner surface of a pneumatic tire and an apparatus employed therefor.
For forming a puncture preventing layer on an inner surface of a pneumatic tire, there has been known a method in which such a layer is formed by a sealing material during molding or after molding of a green or unfinished tire, in which case, however, the green tire is further subjected to vulvanization process, and since such sealing material, if comparatively small in viscosity, tends to become uneven in quality during the vulcanization, it is very difficult to obtain the puncture prevention layer of a predetermined quality. Therefore, depending on the kinds of the sealing materials, such puncture prevention layer should preferably be formed after vulcanization of the green tire. In this case, there may be employed one method in which a sealing material extruded into a sheet-like form is applied onto the inner surface of the tire, and another method in which the sealing material is sprayed onto the inner surface of the tire to form thereon the puncture prevention layer. Although the latter spraying method is preferable due to its simplicity, there are such disadvantages that, in the known high pressure (high temperature) spraying, the sealing material must be in a state close to liquid, and if powder rubber or the like is contained in the sealing material, clogging may result during the spraying, thus the sealing material which can be employed being undesirably limited.
Accordingly, an essential object of the present invention is to provide an improved method of forming puncture preventing layer for a pneumatic tire in which a sealing material extruded even of high viscosity is pulverized into fine particles for being coated under pressure onto an inner surface of a pneumatic tire through centrifugal force, without possibility of clogging during spraying.
Another important object of the present invention is to provide an apparatus which is employable for effecting the puncture preventing layer forming method as described above in an efficient manner.
A further object of the present invention is to provide an apparatus of the above described type which is simple in construction and accurate in functioning, and can be manufactured at low cost.